Evolution, divergence, and convergence in the mandibles of opossums (Didelphidae, Didelphimorphia)

Didelphid marsupials are considered a morphologically unspecialized group with a generalist diet that includes vertebrates,invertebrates,and plant matter.While cranium and scapula variation has alreadybeen examined within Didelphidae,variation inmandible shape,usually associated with diet or phylogeny in other mammalian groups,has not yet been properly assessed in the family.We evaluated the variation in mandible shape and size of didelphids(2470 specimens belonging to 94 species)using 2D geometric morphometrics.We classified the diet of the didel-phids into four broad categories to assess whether morphospace ordination relates to dietary habits.We also provided the most comprehensive phylogeny for the family(i23 out of the 126 living species)using 10 nuclear and mitochondrial genes.We then mapped mandible size and shape onto that phylogeny for 93 selected taxa and ancestral size and shapes were reconstructed by parsimony.We found phylogenetically structured variation in mandible morphology between didelphid groups,and our results indicate that they have a significant phylogenetic signal.The main axis of shape variation is poorly related to size,but the second is strongly allometric,indicating that allometry is not the main factor in shaping morphological diversity on their mandibles.Our results indicate that the shape and size of the ancestral mandible of didelphids would be similar to that of the current species of the genus Marmosa.

Imaging approach for jaw and maxillofacial bone tumors with updates from the 2022 World Health Organization classification

Jaw and maxillofacial bone lesions encompass a wide variety of both neoplastic and non-neoplastic pathologies.These lesions can arise from various tissues,including bone,cartilage,and soft tissue,each presenting distinct challenges in diagnosis and treatment.While some pathologies exhibit characteristic imaging features that aid in diagnosis,many others are nonspecific.This overlap often necessitates a multimodal imaging approach,combining techniques such as radiographs,computed tomography,and magnetic resonance imaging to achieve a diagnosis or narrow the diagnostic considerations.This article provides a comprehensive review of the imaging approach to jaw and maxillofacial bone tumors,including updates on the 2022 World Health Organization classification of these tumors.The relevant anatomy of the jaw and dental structures that is important for accurate imaging interpretation is discussed.

Management of Mandibular Fractures in Children in Ivory Coast: Experience of the Stomatology and Maxillofacial Surgery Department at the University Hospital of Cocody from 2000 to 2019

Introduction: Mandibular fractures in children are becoming increasingly common. Treatment of these fractures is difficult due to their anatomical and physiological complexity. Therefore, there is a need for well-codified management. Our main aim was to develop a decision algorithm for the management of mandibular fractures in children based on our experience. Materials and Methods: This was a retrospective descriptive study carried out in the Department of Stomatology and Maxillofacial Surgery at the University Hospital of Cocody over a period of 20 years (2000-2019). Results: We enrolled 58 patients. The mean age of the patients was 9.35 ± 2.3 years with a sex ratio of 2.22. Traffic accidents were the main cause of mandibular fractures (60.35%). Condylar fractures were the most common (46.87%). Treatment was orthopedic in 45.76% of cases, mixed (orthopedic and surgical) in 24.14% and surgical in 5.17%. Patients were followed up weekly for 1 month, then monthly for 6 months and annually for 3 years, with panoramic radiographs of the maxilla starting at 21 days. We observed 2 cases of complications: temporomandibular ankylosis and gingival stomatitis. Conclusion: Mandibular fractures are common in children. Management is difficult due to anatomical and physiological peculiarities. The choice of treatment depends on several criteria.

Prevalence of Taurodontism in a Tertiary Hospital in Ghana

Background: Taurodontism is one of the most significant deviations from the normal tooth morphology affecting the molars in both primary and permanent dentition. Taurodontism refers to the Enlargement of the pulp chamber, resulting in its bifurcation pushed toward the apex of a tooth’s root. This study evaluated the prevalence of Taurodontism from radiographs taken at the University of Ghana Dental School Oral Radiology Unit from January 2017 to December 2022. Methodology: In this cross-sectional study, panoramic and periapical radiographs of 1000 randomly selected patients who visited the Oral Radiology Unit from January 2017 to December 2022. Radiographs were evaluated for apically displaced pulp chamber. Data was statistically evaluated, and the chi-square test was employed to assess the prevalence of taurodontism in the upper and lower jaws (p Results: Taurodontism was found in 171 radiographs giving it a prevalence of 17.1% of which 57% (98 radiographs) were from females and 43% (73 radiographs) were from males. This finding was not significant (p > 0.05). Taurodontism occurred more in the maxilla (289 teeth, 80.7%) compared to the mandible molars (186 teeth, 64.3%) giving it a ratio of 1.6:1. This finding was highly significant (p Conclusion: Taurodontism is relatively common in the Ghanaian population affecting more females compared to males according to this study. Further studies using a large sample need to be carried out to determine its incidence in the general community.

A Comparative Study of Mandibular Fractures in Senegal: Children vs. Adults

Introduction: The commonest maxillofacial fractures involve the mandible. Age can be considered among influential factors. Aim of the Study: To compare mandibular fractures between children and adults from the beginning up to the treatment in Senegal. Patients and Method: A three-year retrospective study was conducted in a university hospital. The medical records of patients admitted for maxillofacial injuries were reviewed. Patient and injury-related variables including age, gender, etiology, average consultation delay, anatomic location of fracture and treatment were compared up to age of 15 and beyond that. Results: Considering 272 casualties, maxillofacial fractures were less frequent among children than adults (36.7% and 59.7%) and were mainly mandibular (90.1% and 91.4%). Male predilection (sex ratio of 2.4 and 4.9) was twice (2) as pronounced from the age of 16. The average consultation delay was two (2) times shorter for children. Road traffic accidents which predominated among children (33.9%) had comparable frequency (32.3%) although they were outnumbered by assault (37.6%) among adults. Fractures occurred mainly on the corpus (90.1% and 90.4%), particularly on parasymphysis (40.1%) up to the age of 15, whereas angle fractures increased (8.5% to 19.6%) and joint damage decreased afterwards. Intra-oral orthopedic procedures (91.2% and 92.6%) in which mandibular retention splints were more common (37.3%) up to the age of 15 then arch ligatures (49%) were then widely favored. Conclusion: Differences relating to the distribution of causes but also to the anatomic location on the corpus and to the choice of intra-oral orthopedic procedures within overall similarities between children and adults regarding the male predilection, the frequency of road traffic accidents, the mandibular injuries, but also the school therapeutic attitude consisting of favoring the orthopedic option.

A Mathematical Modeling Method Elucidating the Integrated Gripping Performance of Ant Mandibles and Bio-inspired Grippers

The ability to grip unhatched eggs is a skill exploited by the ants Harpegnathos venator,as they care their brood in tunneled nests,which is of extreme difficulty to keep the eggs intact while gripping.In this paper we propose a mathematical modeling method to elucidate the mechanism of such a gripping behavior in the ant mandibles.The new method can be subdivided into following steps.As a preliminary,the concavity geometry and mandible kinematics are examined experimentally.Second,coordinate transformation is used to predict the real-time spatial topology of the concavity.Third,we come up with a new method to quantify the workspace required to grip and the contact area between the concavity and ant egg.Our model indicates that the biaxial rotation fashion with specialized concavities can reduce workspace by 40%and increase contact area by 53%on average compared with the uniaxial rotation pattern,which augments success rate of gentle gripping.This methodology may have applications in evaluating mechanical performance in both natural and artificial grippers.

Is mandible derived mesenchymal stromal cells superior in proliferation and regeneration to long bone-derived mesenchymal stromal cells?

Mesenchymal stromal cells(MSCs)are cells with the characteristic ability of self-renewal along with the ability to exhibit multilineage differentiation.Bone marrow(BM)is the first tissue in which MSCs were identified and BM-MSCs are most commonly used among various MSCs in clinical settings.MSCs can stimulate and promote osseous regeneration.Due to the difference in the development of long bones and craniofacial bones,the mandibular-derived MSCs(M-MSCs)have distinct differentiation characteristics as compared to that of long bones.Both mandibular and long bone-derived MSCs are positive for MSC-associated markers such as CD-73,-105,and-106,stage-specific embryonic antigen 4 and Octamer-4,and negative for hematopoietic markers such as CD-14.

Solitary intraosseous neurofibroma in the mandible mimicking a cystic lesion:A case report and review of literature

BACKGROUND Neurofibromas are benign tumors of a neurogenic origin.If these tumors occur without any other signs of neurofibromatosis,they are classified as isolated neurofibromas.Neurofibromas in the oral cavity mostly occur within soft tissues,indicating that solitary intraosseous neurofibromas in the mandible are rare.Due to the absence of specific clinical manifestations,early diagnosis and treatment of these tumors are difficult to achieve.CASE SUMMARY A 37-year-old female patient visited our hospital due to numbness and swelling of the gums in the right lower molar area that had persisted for half a month.The patient’s overall condition and intraoral examination revealed no significant abnormalities.She was initially diagnosed with a cystic lesion in the right mandible.However,after a more thorough examination,the final pathological diagnosis was confirmed to be neurofibroma.Complete tumor resection and partial removal of the right inferior alveolar nerve were performed.As of writing this report,there have been no signs of tumor recurrence for nine months following the surgery.CONCLUSION This case report discusses the key features that are useful for differentiating solitary intraosseous neurofibromas from other cystic lesions.

Mandibular Embryonal Rhabdomyosarcoma Confused with a Vascular Malformation: About a Case

Malignant mesenchymal tumors (MTM) in children represent 5% to 10% of malignant tumors in children. They constitute a heterogeneous group of tumors of various differentiations depending on their supposed tissue of origin. They mainly include tumors of muscular origin, those derived from connective, vascular, nervous, or adipose tissue. Rhabdomyosarcoma (RMS) is the most common mesenchymal tumor in children and adolescents (60% to 70% of them). And it accounts for 5.8% of all malignant solid tumors in children. Almost half of rhabdomyosarcomas occur in the head and neck. The prognosis for this type of tumor is particularly poor. A case of rhabdomyosarcoma in the mandible with extension to the abdominal wall and unilateral testis in a 6-month-old infant is reported with evolution since birth. It is a purplish lesion at the level under the right chin which was initially taken for vascular malformation, evolving very quickly towards a mandibular mass deforming the painful face with inflammatory signs, followed by the appearance of a hard swelling under the skin on the left flank taking on the same aspect of the mandibular mass. This observation illustrates the need to know how to systematically think about tumor causes in the face of atypical aspects and to carry out an anatomopathological examination.

Clinical and Paraclinical Epidemiological Aspects of Multifocal Fractures of the Mandible in Chuo

Introduction: Multifocal fractures of the mandible are responsible for the modification of anatomy with functional and aesthetic repercussions. The aim of our work is to determine the clinical and paraclinical epidemiological aspects of multifocal mandible fractures. Materials and Methods: Retrospective, descriptive study conducted at the Department of Stomatology and Maxillofacial Surgery of the University Hospital of Owendo, from January 2018 to January 2021. All mandibular multifocal fractures with radiological images were included, while all incomplete records and monofocal fractures were not included. Data collection was done on a form from patient records. Age, sex, mode of transport, periodicity, mechanisms, etiologies, soft tissue lesions, dental joint disorder, sensitivity disorder, dental damage, radiological examination, the number and location of fracture features, and associated lesions were the variables studied. Results: 49 files collected;the average age of 28 ± 8.4 years;male predominance at 75.5%. Personal transport was used at 53%, November was the most accident-prone month, road accident was the dominant etiology at 59%, and direct mechanism at 88%. Stomatoragia predominated at 98%, and hypoaesthesia predominated at 30%. The lesional association with the facial massif was 20%. The CT scan was performed at 61%. The bifocal fracture was the most common at 84%. Discussion: According to Alexander violent assaults are the main cause but for Mala it is MVA. The dental panoramic is the basic examination. For Rocton and Mala, the bifocal fracture is the most frequent of the multifocal fractures. Conclusion: Multifocal fractures are the prerogative of the young subject and road accident is the dominant etiology.

Cemento-ossifying fibroma of the left mandible:A case report

BACKGROUND Ossifying fibroma is a type of benign fibro-osseous lesion.Most lesions affect the mandible region,particularly the molar and pre-molar areas.It predominantly affects females between the second to fourth decades of life.Larger ossifying fibroma tumors require more extensive resection.CASE SUMMARY A 39-year-old female complained of occasional pain and tumor enlargement on her left jaw for the 3 years prior to presentation.Intraoral examination revealed a firm swelling on her left lower gum.Extraoral examination revealed swelling on the left mandible body with no erythema and superficial ulcer.Computed tomography scan revealed a circular-shaped lesion on the patient’s left mandible body with a well-defined radiolucent border,sized 3.2 cm×2.8 cm×0.9 cm.The tumor was removed by marginal mandibulectomy.Biopsy from the resected tumor suggested cemento-ossifying fibroma(COF).CONCLUSION COF is often unnoticed,but this slow-growing tumor can cause significant symptoms regarding its distortion into adjacent structures.

自体下颌瘤骨冷冻再植术

我科于1978～1984年对10例下颌骨肿瘤采用切除患肿瘤的骨段,用液氮冷冻后,原位再植,经10年以上回访效果满意,现报道如下。

Radiation-induced osteosarcoma of the maxilla and mandible after radiotherapy for nasopharyngeal carcinoma

Background:The increasing incidence of radiation-induced osteosarcoma of the maxilla and mandible(RIOSM) has become a significant problem that can limit long-term survival.The purpose of this study was to analyze the association of clinicopathologic characteristics with treatment outcomes and prognostic factors of patients who developed RIOSM after undergoing radiotherapy for nasopharyngeal carcinoma(NPC).Methods:We reviewed the medical records of 53,760 NPC patients admitted to Sun Yat-sen University Cancer Center during the period August 1964 to August 2012.Of these patients,47 who developed RISOM and met inclusion criteria were included in this study.Two of these 47 patients refused treatment and were then excluded.Results:For all patients treated for NPC at Sun Yat-sen University Cancer Center during the study period,the total incidence of RIOSM after radiotherapy was 0.084%(47/53,760).Two patients(4.4%) had metastases at the diagnosis of RIOSM.Thirty-nine of the 45(86.7%) patients underwent surgery for RIOSM;most patients(24/39;61.5%) who underwent resection had gross clear margins,with 15 patients(38.5%) having either a gross or microscopic positive margin.All patients died.The 1-,2-,and 3-year overall survival(OS) rates for the entire cohort of 45 patients were 53.3%,35.6%and 13.5%,respectively.The independent prognostic factors associated with high OS rate were tumor size and treatment type.Conclusions:RISOM after radiotherapy for NPC is aggressive and often eludes early detection and timely intervention.Surgery combined with postoperative chemotherapy might be an effective treatment to improve patient survival.

Establishment of a three-dimensional finite element model for gunshot wounds to the human mandible

Objective:To investigate the feasibility of a finite element model as an ideal research tool for human maxillofacial gunshot wounds.Methods:Mandible CT scan data on the Chinese Visible Human were imported into MIMICS software to obtain the surface mesh of the mandible.Then,these surface-meshed models were imported into ANSA software for automatic net generation.Elements and nodes were partitioned on the basis of the mesh to obtain a three-dimensional finite element model for the mandible with every internal parameter consistent with those of our previously developed model in the pig mandible.The finite element model was imported into LS-DYNA for computation.Finally,the LS-POST was used to complete the simulation and the measurements.Results:A three-dimensional finite element model was successfully established for gunshot wounds in the human mandible.The stress distribution and the degree of injury were simulated dynamically for shots from two types of projectiles in the mandible at one entry angle and at three impact velocities.Conclusion:Three-dimensional finite element models will become ideal research tools for treatment of ballistic wounds of the human maxillofacial region.Using this human mandibular model as a foundation,we will be able to successfully develop three-dimensional finite element models for human maxillofacial gunshot wounds.

Relationship of distraction rate with inferior alveolar nerve degeneration-regeneration shift

Distraction osteogenesis is an important technique for the treatment of maxillofacial abnormities and defects. However, distraction osteo- genesis may cause the injury of the inferior alveolar nerve. The relationship between distraction rate and nerve degeneration-regeneration shift remains poorly understood. In this study, 24 rabbits were randomly divided into four groups. To establish the rabbit mandibular distraction osteogenesis model, the mandibles of rabbits in distraction osteogenesis groups were subjected to continuous osteogenesis dis- traction at a rate of 1.0, 1.5 and 2.0 mm/d, respectively, by controlling rounds of screwing each day in the distractors. In the sham group, mandible osteotomy was performed without distraction, Pin-prick test with a 10 g blunt pin on the labium, histological and histomorpho- metric analyses with methylene blue staining, Bodian＇s silver staining, transmission electron microscopy and myelinated fiber density of inferior alveolar nerve cross-sections were performed to assess inferior alveolar nerve conditions. At 28 days after model establishment, in the pin-prick test, the inferior alveolar nerve showed no response in the labium to a pin pricks in the 2 mm/d group, indicating a severe dysfunction. Histological and histomorphometric analyses indicated that the inferior alveolar nerve suffered more degeneration and in- juries at a high distraction rate （2 mm/d）. Importantly, the nerve regeneration, indicated by newborn Schwann cells and axons, was more abundant in 1.0 and 1.5 mm/d groups than in 2.0 mm/d group. We concluded that the distraction rate was strongly associated with the inferior alveolar nerve function, and the distraction rates of !.0 and 1.5 mm/d had regenerative effects on the inferior alveolar nerve. This study provides an experimental basis for the relationship between distraction rate and nerve degeneration-regeneration shift during dis- traction osteogenesis, and may facilitate reducing nerve complications during distraction osteogenesis.

Dynamic navigation system-guided trans-inferior alveolar nerve implant placement in the atrophic posterior mandible: A case report

BACKGROUND In atrophic posterior mandibular areas,where the bone height superior to the inferior alveolar nerve(IAN)is less than 6 mm,short implants are not applicable.Conventional alternatives such as IAN transposition and various alveolar bone augmentation approaches are technically demanding and prone to complications.CASE SUMMARY Computer-guided dynamic navigation implantation improves the accuracy,predictability,and safety of implant placement.This case report presents a dynamic navigation system-guided trans-IAN implant placement technique,which can successfully treat a posterior mandibular dentition defect when the bone height is only 4.5 mm.The implant was inserted into the buccal side of the IAN and was 1.7 mm away from the IAN.The implantation deviations were controlled within a satisfying range,and the long-term restoration outcome was stable.CONCLUSION Dynamic navigation system-guided trans-IAN implant placement might be a recommended technique for patients with extremely insufficient residual bone height and sufficient bone width in the posterior mandibular area.

Intractable bleeding from solitary mandibular metastasis of hepatocellular carcinoma

Hepatocellular carcinoma （HCC） metastasizes to the mandible is infrequently seen. Solitary bony metastasis to the mandible is rarer. The intractable bleeding caused by rupture of the metastatic HCC is challenging to clinicians. We present a case of a 74-year-old woman with HCC under control without progression for 3 years. Left facial swelling and episodes of bleeding developed recently and biopsy revealed a metastatic HCC. Computer tomography showed a large tumor in parapharyngeal space with evident mandibular ramus destruction. Bleeding occurred from the metastatic tumor but could not be controlled by electrocauterization, SurgicelTM, tissue glue, and bone wax and angiographic embolization. Palliative radiotherapy （2400 cGy in 6 fractions） was tried and the intractable bleeding was successfully stopped after the radiotherapy. Because of the hypervascular and osteolytic nature of the solitary mandibular metastatic lesion, the bleeding was troublesome. Radiotherapy provided successful control of intractable bleeding from the metastatic tumor.

Fixed Bicortical Screw and Blade Implants as a Non-Standard Solution to an Edentulous (Toothless) Mandible

Aim This paper deals with the treatment of an atrophied toothless mandible with a fixing bridge carried by two nonstandard implant systems. Methodology Four bicortical screws were implanted into the frontal part of the mandible and one implant on each side was placed into the distal area of the mandible as a support for a fixing bridge. Results During the years 2002–2007 the authors placed a total of 256 bicortical screw and 84 blade implants. During this period only four bicortical screws and one blade implant failed. The primary and secondary surgical success rate was therefore above 98%, while the prosthetic success rate was 100%. （Bridges which had to be re-fabricated due to implant failure were not taken into account.） Conclusion This approach is recommended as a highly successful and affordable option for a wide range of patients.